The present invention relates to a method and a device for joining workpieces made from plastic, the upper workpiece, facing a laser source, consisting of a material transparent to the laser beam, and the lower workpiece consisting of a material absorbent to the laser beam, such that the mutually bordering contact surfaces for the two workpieces melt and are joined to one another under pressure during a subsequent cooling.
Generally, methods for welding plastics with the aid of a laser beam are known and referred to as transmission welding. It is important for these plastics welding methods that the workpieces are clamped to one another during the welding operation, since an important precondition for a good welded joint of the plastics by means of laser radiation is not only the energy dosing, but also the clean and mechanical contact between the two joint surfaces to be connected to one another. Various methods and devices which permit an adequate contact pressure, in particular with flat parts, are known for the purpose.
It is relatively easy to produce a good clamping condition two-dimensional welding contours. However, as soon as a welding contour is to be set up in three-dimensional form on three-dimensional parts, the mechanical contact of the parts that are to be joined to one another is very difficult to realize technically, particularly when the shape of the parts keeps changing. Both the uniform distribution of the clamping force over the entire contour, and the dosing of the clamping pressure are problematic in this regard.
It is therefore the object of the present invention to propose a possibility which permits contour welding of workpieces made of plastic in three-dimensional form without a special clamping device.